reserve x,y,z for Variable,
  H for ZF-formula,
  E for non empty set,
  a,b,c,X,Y,Z for set,
  u,v,w for Element of E,
  f,g,h,i,j for Function of VAR,E;

theorem Th10:
  not x in Free H & E,f |= H implies E,f |= All(x,H)
proof
A1: len H = len H;
  for n being Nat holds Lm2[n] from NAT_1:sch 4(Lm1);
  hence thesis by A1;
end;
